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P 1, 1964 G. F. w. GARBE 3,146,581

"D" JEWEL WATCH ESCAPEMENT Filed Dec. 26, 1961 4 Sheets-Sheet 1 ATTORNEYS Sept. 1, 1 G. F. w. GARBE "D" JEWEL WATCH ESCAPEMENT 4 Sheets-Sheet 2 Filed Dec. 26, 1961 &

INVENTOR. GEORGE FRIEDRICH WILHELM GHRBE mm R 9 7 BY Dam/HM W ATTORNEYS P 1964 G. F. w. GARBE 3,146,581 "D" JEWEL WATCH ESCAPEMENT 4 Sheets-Sheet 5 Filed Dec. 26, 1961 Tij.E3-

INVENTOR. GEORGE FRIEDRICH WILHELM Gears:

BY M,M -W*W ATTORNEYS Sept. 1, 1964 G. F. w. GARBE 3,146,581

"D" JEWEL WATCH ESCAPEMENT Filed Dec. 26, 1961 4 Sheets-Sheet 4 INVENTOR. GEORGE FElEDRlCH Wumzm GHEBE Q'T'TORNEVQ United States Patent 3,146,581 D JEWEL WATCH ESCAPEIVENT George Friedrich Wilhelm Garbe, Waterbury, Conn, assignor to The United States Time Corporation, Middlebury, Conn., a corporation of Connecticut Filed Dec. 26, 1961, Ser. No. 161,784 1 Claim. (Cl. 58-422) The present invention relates to timekeeper movements and more particularly to a novel escapement.

A timekeeper escapement controls the release of power from a source such as a mainspring so that the power is delivered in a continuous and regulated series of periodic impulses. The accuracy and efficiency of the escapement movement are important determinants of the quality of the Watch.

The lever escapement is the type presently used in almost all pocket and wrist watches. A lever escapement in common use consists of a toothed escape wheel connected through a gear train to receive power from the mainspring or other power source; a lever (or pallet) pivoted about a point between its ends, the pivot being at a point outside the periphery of the escape wheel, the lever having at one end a fork and at the other end a pair of arms forming a T, with each arm carrying a pallet jewel which moves in time with the lever, the jewels being separated by a distance determined by the distance be tween the teeth of the escape wheel according to a generally accepted formula; and a balance wheel which pivots on the balance staff and which carries a roller jewel (or impulse pin). The balance wheel is centered on the balance staff and to it is attached the hairspring.

When the watch is not in operation, as for instance when the mainspring is almost unwound, one of the jewels is between two teeth of the escape wheel, locking it against rotation. Once the mainspring is wound and the jewel removed from its locking position, the process of controlled release of the power of the mainspring begins. The escape wheel, driven by the mainspring through its gear train, is impelled against the jewel that has been locking it against rotation. The jewel moves up from the center of the wheel, rocking the lever. The forked part of the lever is impelled against the roller jewel, causing the balance wheel to rotate and to put the hairspring under tension. The hairspring then springs back, causing rotation of the balance wheel in the opposite direction and causing the roller jewel to strike the forked portion of the lever arm. The lever turns about its pivot, causing one of its two jewels to drop between two teeth of the escape wheel, temporarily locking the wheel against further rotation.

A lever escapement of this type requires a means to limit the swing of the lever. One such common means is the use of banking pins, one pin being positioned on each side of the lever. Another such meanswhich has been suggested but rarely used is a banking surface on each tooth of the escape wheel which the jewel will hit if it goes to the limit of its movement toward the center of the wheel. Another requirement is positive drawing of the lever arm toward the wheels center by cam action of each tooth of the escape wheel and each jewel to ensure that a jewel will stay in the lock position until moved away by the roller jewel, causing the lever to rotate. This cam action can be controlled byacam surface on either tooth or jewel. A further requirement is uniform positioning and interchangeability of jewels. One way to provide this last requirement is to use a jewel shaped in the form of a D as set forth in De Long Patent 1,327,226.

Heretofore great care and expense have been required to ensure that the parts described above have the proper size, proportion and position relative to each other in order to achieve accurate and efficient performance. One

Patented Sept. 1, 1964 circumstance which can prevent such performance is wide variation in the amount of draw of a tooth on a jewel from the point where the two meet to the point where draw is completed. The draw is created on the face of the jewel, if the cam surface is on the jewel and the draw is created on the face of the tooth, if the cam surface is on the tooth. The amount of draw is defined by a draw angle which has a technical definition explained later. Another such circumstance which can prevent accurate and efficient performance is incorrect location of the jewel due to improper placement of it on the lever or to its being bent, the result being that a jewel is likely to contact a tooth improperly and jam the escapement. Another problem is to ensure that each tooth gives each jewel maximum impulse for, maximum efficiency. Another problem is that lubrication may either move away from the parts to be lubricated, or become sticky and slow the performance of the watch. This problem is especially acute in the area where the jewel hits the tooth at the banking surface of the tooth. It is also acute in the area on the lock face of the tooth because current D jewels are made with sharp corners in order to obtain maximum impulse.

It is an objective of the present invention to improve performance as to accuracy and efficiency without increasing the care and expense required to ensure proper size, proportion and relative position of the parts. According to my invention, this improvement is achieved by providing a D-jewel escapement with cam surface on the tooth for drawing the lever downward so that drawing can be accurately controlled and variation in draw over the course of travel of the jewel be minimized; by departing from the generally accepted formula determining the distance between jewels; by giving each jewel a novel contour to decrease wear without decreasing the effective length of the jewels face which contacts the tooth to give an impulse to the balance wheel; and by giving the banking surface a particular contour not only to control the swing of the lever without utilizing external banking pins and to prevent jamming the escapement if the watch is jarred or roughly cleaned but also to provide an oil reservoir to provide the proper amount of lubrication.

A preferred embodiment of the escapement of the present invention is described below in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic top plan view of the conventional type of lever escapement movement having rectangular jewels which is included in order to explain the terms used herein and the nature of the present invention;

FIG. 2 is a schematic top plan view of the escapement of the present invention;

FIG. 3 is a top plan layout drawing of the escapement of the present invention; and

FIGS. 4-8 are schematic top plan views showing the relationships of the jewels to the teeth in the course of the levers movement.

In the prior art of FIG. 1, the escape wheel 1 is connected through a gear train (not shown) to the barrel of the mainspring. If the escape wheel is not stopped, it will rotate the gear train at full speed until the mainspring is completely unwound. The escape wheel 1 is prevented from such free rotation by the action of the generally T-shaped lever 2 which pivots about the shaft (axle) 3. The upright standing pallet jewels 4 (entrance) and 5 (exit) are, in this type of escapement, rectangularly shaped and are connected to each of the two arms of the lever 2. The lever 2 has a fork-like portion 6 at its top which comprises a left fork 7 and its horn 7a and a right fork 8 and its horn 8a. The notch formed by the two forks is adapted to fit over an upright standing roller jewel 9 which is inserted into the spoke of the balance wheel 10 or into the great roller disc (not shown). A

roller 11, known as a safety roller, is fastened under the balance wheel and pivots on the balance staff 12 to prevent the lever from becoming loosened from the escape ment. The indented crescent portion 11a of the roller 11 allows the roller to pass when the lever is unlocked and approach its control position. The banking pins 23 and 23a on opposite sides of lever 2 limit the swing of the lever.

The exit pallet jewel is shown in its locked position. The escape wheel is prevented from turning in its normal clockwise motion by the face 13 of the pallet jewel 5 being held against the heeel (point) 14 of tooth 15. The teeth are undercut at 39. In this position, the movement of the tooth draws the pallet jewel 5 toward the center of the escape wheel. The cam face (in this case it is on the left face of the jewel which comes in contact with the tooth) which determines how much of the movement has this draw effect, is herein called the draw face. The lock face is that portion of the jewel or tooth which prevents the wheel from turning by holding against the point of the tooth or jewel, respectively. In the rectangular pallet jewel escapement of FIG. 1, the lock face and the draw face are both on the jewel.

FIGS. 2-6 show the improved escapement of the present invention in which the escape wheel 1 includes a special curved surface (resilient curve) 21 herein called a banking surface, which controls the extent of swing of the lever 2. This eliminates back bounce caused by the lever striking the banking pins. In addition, in the escapement of this invention, the banking surface has adjacent to its corner 22 a portion 51 with an outwardly curved radius. This outward curved radius, acting against the curved corner 28 of the jewel, insures that there is only line and not surface contact between the jewel and the banking surface, and also insures that the banking surface and the jewel surface fall away rapidly from each other. Minimizing surface of contact avoids the possibility of adhesion or stickiness between the jewel and the wheel due to thickening of the lubricating oil. The curve surface 51 also insures that there is an oil reservoir of the proper size and shape at the corner 22. If the oil reservoir is of improper size and shape, the oil will either move away from it too readily or will dry up and become sticky.

The escape wheel 1 has, preferably, fifteen club teeth 25. The teeth are alike and the jewels are alike.

The jewels 26 and 27 are in the form of currently used D-shaped jewels, except for one departure from current practice, i.e., a round surface where the circular part of the D meets the fiat part. This departure is significant. In the case of D-shaped jewels in current use, the jewel as installed has a corner, causing undue wear of the face of the tooth and causing imperfect and inefficient contact be tween tooth impulse face and jewel. The reason for this imperfect contact is that the provision for draw, described above, necessarily introduces an additional factor, i.e., that when the balance wheel unlocks the lever and jewel from the lock position and raises the jewel upward, the wheel 1 is rotated a certain angle backward. The heel of the tooth strikes the impulse face at a certain angle which varies somewhat in each watch. At the first moment of impulse, the angle is the same regardless of the shape of the jewels corner and no impulse will be given until a certain critical angle is attained. Regardless of the shape of the corner, the angular relationship results in the effective pushing contact between the jewel and heel 14 being attained at some position52 somewhat toward the center of the jewels impulse face, see FIG. 3.

According to my invention, I depart from current practice by providing a rounded corner on each jewel. The use of the rounded corner does not result in a loss of impulse as has been generally believed because the heel rarely, if ever, contacts the jewel at the jewels corner with much force. The round corner does not wip off oil from the face of the tooth, as Sometimes occurs with jewels having sharp corners. It also decreases wear on the draw face of the tooth. A

The D jewels are positioned on the lever so that when each jewel is in its locking and drawing positions the corner of the jewel slides against the face of the tooth. The length of the draw movement and the length of the draw face is measured as between lines 35 and 35a taken from the pivot point 3 of the lever 2 (see FIG. 3). The cam surface controlling the draw, i.e., the draw face is on the tooth rather than on the jewel. When the draw face is on the tooth, the quantititive effect of the cam surface to control the drawing action, i.e., the draw angle of the tooth, is measured by drawing a line 30 from the center 29 of the escape wheel to the heel 14 of the tooth and then drawing another line 31 from the heel 14 of the tooth along the face of the tooth and striking angle 32, the draw angle, between the lines 30 and 31. I have found that for best performance the draw angle should be between 10 and 16.

The angle that the direction of movement of a jewel makes with a tooth draw face is an important factor in symmetry of movement and therefore in accuracy. If variation in this angle can be minimized, it means there will be a minimum variation in the movement of the lever. That angle may be determined as in the following examples shown in FIG. 3. In the case of the entrance jewel 26 at its outermost point of contact 48 with heel 14, that angle is determined by inscri-bing a line 48a from lever pivot 3 to the point 48. A line 36 perpendicular to the line 48a is then drawn at that point of contact. A line 37 is then taken from the point of contact 48 along the draw face of the tooth. The angle under discussion is the angle between lines 36 and 37, i.e., angle 45. In the example of jewel 26, at its outermost point of contact it is 1045. Measured in the same way, the angle under discussion for the entrance jewel at its innermost position 49 is 14, with line 36a corresponding to line 36 and the line 37a corresponding to line 37. Since the draw surface of the tooth is straight, the draw angle on the toothvaries only in. an amount which is parctically equal to the angle between the lines 36a and 36.

For the exit jewel 27 at its outermost contact position,

the angle under discussion is determined in the same way to be 13 20' (angle 46) and for the exit jewel at its innermost position 1055 (angle 46a). The average of the extremes for the entrance jewel, 1222, and the average of the extremes of the exit jewel, 1207, are substantially equal, providing substantially symmetrical movement.

The distance at the outermost part of the swing of the lever from the topmost portion of the tooth to the jewel portion nearest the center of the escape wheel, herein called the drop clearance, is equal for each jewel. This equal drop clearance, a further departure from current practice, is attained in the escapement by a particular spacing of the jewels from each other on the lever arm.

In current practice, the generally accepted formula is that the jewels are to span 2 /2 teeth. To span 2 /2 teeth they must be apart on the wheel. The present escapement,

- however, gives the jewels a span of 60 and 24 minutes taken between lines 33 and 34, i.e., measuring from the left edge of the left pallet jewel to the left edge of the right pallet jewel. At the moment when each jewel leaves its lock face and is about to slide over the impulse face, it is 30 and 12 from the line through the escape wheel center 29 and the lever pivot 3. It is required for this spacing that the jewels should be spaced further apart by from 5 minutes to 2, and preferably from 5 minutes to 1, than the spacing according to the formula 360 (number of teeth) number of teeth spanned by the jewels locking corners 28 and 38 of the jewels are the same distance from the lever pivot point 3. The impulse, as in other club tooth movements, is divided between the impulse -face 24, the crown of the tooth and the impulse face 40, the bottom portion of the jewel.

In operation, as shown in FIGS. 4-8, the entrance jewel 26 starts its descent (FIG. 4), comes into contact with the heel 14 of the tooth (FIG. 5), is pulled down into corner 22 and into lock position by the draw face of the tooth (FIG. 6), and is then lifted from its lock position by the return swing of the lever (FIG. 7). In FIG. 8 the heel 14 is given an impulse to the bottom face of jewel 27. As in conventional club tooth movements, the impulse face of the tooth and jewel are at an angle to each other to lessen friction.

It should be noted that the jewels of my escapement have equal lock, equal drop clearance and equal average angle between direction of movement of jewel and the face of the tooth, thereby providing a substantially symmetrical movement.

I claim:

A timepiece lever escapement comprising a pivoted lever with an entrance and an exit pallet member, an escape wheel having a plurality of club teeth having impulse and draw faces coacting with the said pallet members, a reciprocating balance wheel capable of causing the lever to pivot and thereby to control the rate of rotation of the escape wheel, said escape wheel having the draw faces of its teeth inclined in the direction of its rotation to provide a draw angle on the teeth, said members being D shaped in cross-section in a plane parallel to the plane of the lever, each with a straight impulse face and the remaining surface rounded and each D shaped member having its rounded surface and its impulse face meeting at a rounded corner, and said members being inclined at a predetermined angle so that during the draw the direction of movement of the members is determined entirely by the camming action of the tooths draw angle and so that as the lever pivots and carries each pallet member into the path of each successive tooth the member in the path of the said tooth is drawn and locked against the draw face of the said tooth, said pallet members being separated on the lever at a distance in degrees measured from the outside of the entrance member to the inside of the exit member and from the center of the escape wheel greater by from 5 minutes to 2 than the distance determined by the formula number of teeth spanned (number of teeth) by the members References Cited in the file of this patent UNITED STATES PATENTS 593,849 Lane Nov. 16, 1897 1,327,226 De Long Jan. 6,1920

FOREIGN PATENTS 101,260 Austria Oct. 10, 1925 682,436 Great Britain Nov. 12, 1952 1,045,163 France June 24, 1954 

